﻿using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
using System.Windows.Threading;

namespace rssappbar
{
    public enum ABEdge : int
    {
        Left,
        Top,
        Right,
        Bottom,
        None
    }

    internal static class AppBarFunctions
    {
        [StructLayout(LayoutKind.Sequential)]
        private struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;
            public RECT(Rect r)
            {
                Left = (int)r.Left;
                Right = (int)r.Right;
                Top = (int)r.Top;
                Bottom = (int)r.Bottom;
            }
            public static bool operator ==(RECT r1, RECT r2)
            {
                return r1.Bottom == r2.Bottom && r1.Left == r2.Left && r1.Right == r2.Right && r1.Top == r2.Top;
            }
            public static bool operator !=(RECT r1, RECT r2)
            {
                return !(r1 == r2);
            }
            public override bool Equals(object obj)
            {
                return base.Equals(obj);
            }
            public override int GetHashCode()
            {
                return base.GetHashCode();
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct APPBARDATA
        {
            public int cbSize;
            public IntPtr hWnd;
            public int uCallbackMessage;
            public int uEdge;
            public RECT rc;
            public IntPtr lParam;
        }

        private enum ABMsg : int
        {
            ABM_NEW = 0,
            ABM_REMOVE,
            ABM_QUERYPOS,
            ABM_SETPOS,
            ABM_GETSTATE,
            ABM_GETTASKBARPOS,
            ABM_ACTIVATE,
            ABM_GETAUTOHIDEBAR,
            ABM_SETAUTOHIDEBAR,
            ABM_WINDOWPOSCHANGED,
            ABM_SETSTATE
        }
        private enum ABNotify : int
        {
            ABN_STATECHANGE = 0,
            ABN_POSCHANGED,
            ABN_FULLSCREENAPP,
            ABN_WINDOWARRANGE
        }

        private enum TaskBarPosition : int
        {
            Left,
            Top,
            Right,
            Bottom
        }

        [StructLayout(LayoutKind.Sequential)]
        class TaskBar
        {
            public TaskBarPosition Position;
            public TaskBarPosition PreviousPosition;
            public RECT Rectangle;
            public RECT PreviousRectangle;
            public int Width;
            public int PreviousWidth;
            public int Height;
            public int PreviousHeight;
            public TaskBar()
            {
                Refresh();
            }
            public void Refresh()
            {
                APPBARDATA msgData = new APPBARDATA();
                msgData.cbSize = Marshal.SizeOf(msgData);
                SHAppBarMessage((int)ABMsg.ABM_GETTASKBARPOS, ref msgData);
                PreviousPosition = Position;
                PreviousRectangle = Rectangle;
                PreviousHeight = Height;
                PreviousWidth = Width;
                Rectangle = msgData.rc;
                Width = Rectangle.Right - Rectangle.Left;
                Height = Rectangle.Bottom - Rectangle.Top;
                int h = (int)SystemParameters.PrimaryScreenHeight;
                int w = (int)SystemParameters.PrimaryScreenWidth;
                if (Rectangle.Bottom == h && Rectangle.Top != 0) Position = TaskBarPosition.Bottom;
                else if (Rectangle.Top == 0 && Rectangle.Bottom != h) Position = TaskBarPosition.Top;
                else if (Rectangle.Right == w && Rectangle.Left != 0) Position = TaskBarPosition.Right;
                else if (Rectangle.Left == 0 && Rectangle.Right != w) Position = TaskBarPosition.Left;
            }
        }

        [DllImport("SHELL32", CallingConvention = CallingConvention.StdCall)]
        private static extern uint SHAppBarMessage(int dwMessage, ref APPBARDATA pData);

        [DllImport("User32.dll", CharSet = CharSet.Auto)]
        private static extern int RegisterWindowMessage(string msg);

        private class RegisterInfo
        {
            public int CallbackId { get; set; }
            public bool IsRegistered { get; set; }
            public Window Window { get; set; }
            public ABEdge Edge { get; set; }
            public ABEdge PreviousEdge { get; set; }
            public WindowStyle OriginalStyle { get; set; }
            public Point OriginalPosition { get; set; }
            public Size OriginalSize { get; set; }
            public ResizeMode OriginalResizeMode { get; set; }


            public IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam,
                                    IntPtr lParam, ref bool handled)
            {
                if (msg == CallbackId)
                {
                    if (wParam.ToInt32() == (int)ABNotify.ABN_POSCHANGED)
                    {
                        PreviousEdge = Edge;
                        ABSetPos(Edge, PreviousEdge, Window);
                        handled = true;
                    }
                }
                return IntPtr.Zero;
            }

        }
        private static Dictionary<Window, RegisterInfo> s_RegisteredWindowInfo
            = new Dictionary<Window, RegisterInfo>();
        private static RegisterInfo GetRegisterInfo(Window appbarWindow)
        {
            RegisterInfo reg;
            if (s_RegisteredWindowInfo.ContainsKey(appbarWindow))
            {
                reg = s_RegisteredWindowInfo[appbarWindow];
            }
            else
            {
                reg = new RegisterInfo()
                {
                    CallbackId = 0,
                    Window = appbarWindow,
                    IsRegistered = false,
                    Edge = ABEdge.None,
                    PreviousEdge = ABEdge.None,
                    OriginalStyle = appbarWindow.WindowStyle,
                    OriginalPosition = new Point(appbarWindow.Left, appbarWindow.Top),
                    OriginalSize =
                        new Size(appbarWindow.ActualWidth, appbarWindow.ActualHeight),
                    OriginalResizeMode = appbarWindow.ResizeMode,
                };
                s_RegisteredWindowInfo.Add(appbarWindow, reg);
            }
            return reg;
        }

        private static void RestoreWindow(Window appbarWindow)
        {
            RegisterInfo info = GetRegisterInfo(appbarWindow);

            appbarWindow.WindowStyle = info.OriginalStyle;
            appbarWindow.ResizeMode = info.OriginalResizeMode;
            appbarWindow.Topmost = false;

            Rect rect = new Rect(info.OriginalPosition.X, info.OriginalPosition.Y,
                info.OriginalSize.Width, info.OriginalSize.Height);
            appbarWindow.Dispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle,
                    new ResizeDelegate(DoResize), appbarWindow, rect);

        }


        public static void SetAppBar(Window appbarWindow, ABEdge edge)
        {
            RegisterInfo info = GetRegisterInfo(appbarWindow);
            info.Edge = edge;

            APPBARDATA abd = new APPBARDATA();
            abd.cbSize = Marshal.SizeOf(abd);
            abd.hWnd = new WindowInteropHelper(appbarWindow).Handle;

            if (edge == ABEdge.None)
            {
                if (info.IsRegistered)
                {
                    SHAppBarMessage((int)ABMsg.ABM_REMOVE, ref abd);
                    info.IsRegistered = false;
                }
                RestoreWindow(appbarWindow);
                info.PreviousEdge = info.Edge;
                return;
            }

            if (!info.IsRegistered)
            {
                info.IsRegistered = true;
                info.CallbackId = RegisterWindowMessage("AppBarMessage");
                abd.uCallbackMessage = info.CallbackId;

                uint ret = SHAppBarMessage((int)ABMsg.ABM_NEW, ref abd);

                HwndSource source = HwndSource.FromHwnd(abd.hWnd);
                source.AddHook(new HwndSourceHook(info.WndProc));
            }

            appbarWindow.WindowStyle = WindowStyle.None;
            appbarWindow.ResizeMode = ResizeMode.NoResize;
            appbarWindow.Topmost = true;

            ABSetPos(info.Edge, info.PreviousEdge, appbarWindow);
        }

        private delegate void ResizeDelegate(Window appbarWindow, Rect rect);
        private static void DoResize(Window appbarWindow, Rect rect)
        {
            appbarWindow.Width = rect.Width;
            appbarWindow.Height = rect.Height;
            appbarWindow.Top = rect.Top;
            appbarWindow.Left = rect.Left;
        }

        static TaskBar tb = new TaskBar();

        private static void ABSetPos(ABEdge edge, ABEdge prevEdge, Window appbarWindow)
        {
            APPBARDATA barData = new APPBARDATA();
            barData.cbSize = Marshal.SizeOf(barData);
            barData.hWnd = new WindowInteropHelper(appbarWindow).Handle;
            barData.uEdge = (int)edge;
            RECT wa = new RECT(SystemParameters.WorkArea);
            tb.Refresh();
            switch (edge)
            {
                case ABEdge.Top:
                    barData.rc.Left = wa.Left - (prevEdge == ABEdge.Left ? (int)Math.Round(appbarWindow.ActualWidth) : 0);
                    barData.rc.Right = wa.Right + (prevEdge == ABEdge.Right ? (int)Math.Round(appbarWindow.ActualWidth) : 0);
                    barData.rc.Top = wa.Top - (prevEdge == ABEdge.Top ? (int)Math.Round(appbarWindow.ActualHeight) : 0) - ((tb.Position != TaskBarPosition.Top && tb.PreviousPosition == TaskBarPosition.Top) ? tb.Height : 0) + ((tb.Position == TaskBarPosition.Top && tb.PreviousPosition != TaskBarPosition.Top) ? tb.Height : 0);
                    barData.rc.Bottom = barData.rc.Top + (int)Math.Round(appbarWindow.ActualHeight);
                    break;
                case ABEdge.Bottom:
                    barData.rc.Left = wa.Left - (prevEdge == ABEdge.Left ? (int)Math.Round(appbarWindow.ActualWidth) : 0);
                    barData.rc.Right = wa.Right + (prevEdge == ABEdge.Right ? (int)Math.Round(appbarWindow.ActualWidth) : 0);
                    barData.rc.Bottom = wa.Bottom + (prevEdge == ABEdge.Bottom ? (int)Math.Round(appbarWindow.ActualHeight) : 0) - 1 + ((tb.Position != TaskBarPosition.Bottom && tb.PreviousPosition == TaskBarPosition.Bottom) ? tb.Height : 0) - ((tb.Position == TaskBarPosition.Bottom && tb.PreviousPosition != TaskBarPosition.Bottom) ? tb.Height : 0);
                    barData.rc.Top = barData.rc.Bottom - (int)Math.Round(appbarWindow.ActualHeight);
                    break;
            }

            SHAppBarMessage((int)ABMsg.ABM_QUERYPOS, ref barData);
            switch (barData.uEdge)
            {
                case (int)ABEdge.Bottom:
                    if (tb.Position == TaskBarPosition.Bottom && tb.PreviousPosition == tb.Position)
                    {
                        barData.rc.Top += (tb.PreviousHeight - tb.Height);
                        barData.rc.Bottom = barData.rc.Top + (int)appbarWindow.ActualHeight;
                    }
                    break;
                case (int)ABEdge.Top:
                    if (tb.Position == TaskBarPosition.Top && tb.PreviousPosition == tb.Position)
                    {
                        if (tb.PreviousHeight - tb.Height > 0) barData.rc.Top -= (tb.PreviousHeight - tb.Height);
                        barData.rc.Bottom = barData.rc.Top + (int)appbarWindow.ActualHeight;
                    }
                    break;
            }
            SHAppBarMessage((int)ABMsg.ABM_SETPOS, ref barData);

            Rect rect = new Rect((double)barData.rc.Left, (double)barData.rc.Top, (double)(barData.rc.Right - barData.rc.Left), (double)(barData.rc.Bottom - barData.rc.Top));
            appbarWindow.Dispatcher.BeginInvoke(new ResizeDelegate(DoResize), DispatcherPriority.ApplicationIdle, appbarWindow, rect);
        }
    }
}
